The xps program displays and continuously updates in an X Window the
Unix processes as a tree or forest. The roots of the tree are on the
left-hand side and the leaf processes (with no children) are on the
right-hand side. The status of each process (running, sleeping,
stopped, etc.) can be indicated by a color. Different users can appear
as different colors too.

Within each level, processes are grouped so that those with the same
parent process id are grouped together. Within this, processes are
arranged by userid with lower number uid's appearing towards the
top. In general, the order of children is the order in which they were
spawned, with the older processes appearing towards the top.

In contrast to pstree and many tree-widget based programs, the overall
tree display uses diagonal lines; some effort is made to effectively
use the full 2-dimensional area of the screen by balancing levels and
centering the children of a node between their parent. A goal of the
program is to visually give a picture of what's going on. So when
possible processes are kept close to their parents so one needn't
scroll around too much and so that there isn't a lot of redrawing as
processes are created or destroyed.

One can click on a process to get more information (via ps) about that
process, send a signal to the process, or set its priority, assuming
you have the permission to do so. Since programs of this ilk can
consume a bit of CPU on their own, some effort has been made to turn
off the update process when the program is iconified or not
visible.
